Polycarbonates are known as being tough and having good film-forming properties which result in tough, strong polymer layers. Some polycarbonates having recurring carboxyl components are used in applications requiring hardness, elasticity and flexibility. Other polycarbonates having recurring alkylidene diphenylene components are used as binders in electrophotographic layers of as supports in silver halide containing photographic elements.
However, polycarbonates are hydrophobic and layers of polycarbonates are generally coated from organic solvents. Coating from organic solvents results in layers which are impermeable to water. Such layers are unsuited for use in hydrophilic photographic layers.
Emulsification of polycarbonates using surfactants and water-immiscible organic solvents or direct mechanical shearing of water-polycarbonate mixtures at high temperatures require excessive amounts of surfactants, or risk degradation and decomposition of the polycarbonate dispersions. The problem is that the particle size of the polycarbonates in such emulsions is so large as to be unsuitable for use in the hydrophilic layers such as are used in photographic elements.